django/docs/howto/deployment/asgi/index.txt

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=======================
How to deploy with ASGI
=======================
As well as WSGI, Django also supports deploying on ASGI_, the emerging Python
standard for asynchronous web servers and applications.
.. _ASGI: https://asgi.readthedocs.io/en/latest/
Django's :djadmin:`startproject` management command sets up a default ASGI
configuration for you, which you can tweak as needed for your project, and
direct any ASGI-compliant application server to use.
Django includes getting-started documentation for the following ASGI servers:
.. toctree::
:maxdepth: 1
daphne
hypercorn
uvicorn
The ``application`` object
==========================
Like WSGI, ASGI has you supply an ``application`` callable which
the application server uses to communicate with your code. It's commonly
provided as an object named ``application`` in a Python module accessible to
the server.
The :djadmin:`startproject` command creates a file
:file:`<project_name>/asgi.py` that contains such an ``application`` callable.
It's not used by the development server (``runserver``), but can be used by
any ASGI server either in development or in production.
ASGI servers usually take the path to the application callable as a string;
for most Django projects, this will look like ``myproject.asgi:application``.
.. warning::
While Django's default ASGI handler will run all your code in a synchronous
thread, if you choose to run your own async handler you must be aware of
async-safety.
Do not call blocking synchronous functions or libraries in any async code.
Django prevents you from doing this with the parts of Django that are not
async-safe, but the same may not be true of third-party apps or Python
libraries.
Configuring the settings module
===============================
When the ASGI server loads your application, Django needs to import the
settings module — that's where your entire application is defined.
Django uses the :envvar:`DJANGO_SETTINGS_MODULE` environment variable to locate
the appropriate settings module. It must contain the dotted path to the
settings module. You can use a different value for development and production;
it all depends on how you organize your settings.
If this variable isn't set, the default :file:`asgi.py` sets it to
``mysite.settings``, where ``mysite`` is the name of your project.
Applying ASGI middleware
========================
To apply ASGI middleware, or to embed Django in another ASGI application, you
can wrap Django's ``application`` object in the ``asgi.py`` file. For example::
from some_asgi_library import AmazingMiddleware
application = AmazingMiddleware(application)